Saws and other apparatuses designed for cutting or performing other working operations on a workpiece typically include mechanisms for setting the saw blade or cutting tool in selected angular relationships with the workpiece when performing various cutting operations. Examples include chop-type compound miter saws adapted for allowing the user to selectively set the saw blade at any of a number of positions or modes for square cutting, miter cutting, bevel cutting, or even compound miter cutting in which combination miter angle and bevel angle cutting operations are performed on the workpiece. In addition, some operations, such as dado cutting, groove cutting, or shaping operations, for example, require the use of saw blades or other cutting or working devices of different shapes or sizes to be substituted for one another in order to perform the desired operation on the workpiece. In these instances, the saw or cutting device must be capable of cross-cutting or sliding movement of the blade or cutting tool in lieu of, or in addition to, chop-type engagement with the workpiece.
In order to allow for the setting of miter and bevel angles, the saw blade, cutter or other working device is angularly adjustable with respect to both a horizontal base and a vertical fence against which the workpiece is positioned. The miter adjustment allows the saw blade, cutter or other working device to be angularly positioned with respect to the vertical fence while maintaining perpendicularity with the horizontal base. The bevel adjustment allows the saw blade, cutter or other working device to be angularly positioned with respect to the horizontal base while maintaining perpendicularity with the vertical fence. Various combinations of miter angles and bevel angles are accomplished by simultaneously adjusting the angularity of the blade with respect to both the horizontal base and the vertical fence.
In any of these cutting operations whether they are performed on chop-type, cross-cut, or combination type devices, a blade guard mechanism must be capable of exposing a sufficient portion of the blade to perform the desired cutting operation, while at the same time adequately protecting the operator during cutting and when the blade is in an at-rest position. Such a guard mechanism also should preferably protect the guard from damage in the event of a bent or deflected blade or cutter during such operations, should prevent the blade or cutter from vibrating loose from or on its arbor shaft during such operations, and should allow for maximum user comfort and control when performing such operations. Preferably, undesired operation of the saw or other such device should be prevented when in a storage or inoperative state.
Unfortunately, many conventional devices have proved to be deficient in meeting some or all of these objectives, or have required burdensome multiplicities of parts or components in order to achieve them. Thus, many of such conventional devices have also often been found to be heavy and overly complex, difficult and expensive to design, manufacture and maintain, as well as requiring large spaces in which to operate them. In some cases, meeting these objectives has also resulted in unduly limiting cutting capacities.
In accordance with the present invention, a blade or cutter guard mechanism preferably includes an upper guard that is fixed relative to a drive assembly for the arbor shaft of the blade or cutter and a lower guard that is pivotally movable relative to the fixed upper guard. Preferably, a guard-actuating linkage assembly includes a first link having an inner end pivotally interconnected with a housing assembly upon which the drive assembly is pivotally mounted in order to move the blade and drive assembly into engagement with the workpiece. An opposite intermediate end of the first link is pivotally interconnected with an intermediate end of yet another, second link whose opposite outer end is pivotally and drivingly interconnected with the movable guard. An intermediate roller or roller assembly is rotatably interconnected with the interconnected intermediate ends of the links and is engageable with a cam surface at a fixed location formed on the drive assembly and thus fixed relative to the fixed guard. The shape and position of the cam surfaces are pre-designed to control the rate of movement of movable guard as the saw blade or cutter is moved between non-cutting and cutting positions. In a preferred form of this guard arrangement, the moveable guard can be manually moved for overriding pivotal movement irrespectively and independently of the position of the blade and drive assembly relative to the workpiece.
A return spring can be advantageously included in the guard linkage assembly for resiliently biasing the movable guard toward a normally closed position covering a maximum portion of the cutting periphery of the blade or cutter. Such return spring is preferably a torsional coil spring with one anchoring end or leg interconnected with the fixed guard or drive assembly (at a fixed location thereon) and an opposite end or leg interconnected with the movable guard (also at a fixed location thereon). An off-center spring enclosure, which is radially offset relative to the arbor shaft, is preferably included for restricting radial expansion of the torsional spring to directions away from the workpiece (on opposite sides of the arbor shaft from the workpiece) in order to maximize the workpiece cutting depth capacity of the saw blade or cutter.
Another optional but preferred feature of the invention is an arbor shaft cover that is pivotally interconnected with the fixed guard and that substantially prevents or minimizes any tendency of the arbor shaft nut, screw or other blade-securing fastener to work loose on, or free of, the arbor shaft. Such arbor cover can be pivoted out of the way to allow blade removal or blade changing by way of a releasable cover retaining fastener at one end of the pivotal cover, with such retaining fastener also optionally being configured to extend axially inside the fixed guard when tightened so as to act as one of a pair of blade calipers axially spaced from opposite sides of the blade or cutter. Such calipers thereby prevent or substantially minimize damage to the fixed guard in the event of a bent or deflected blade or cutter.
A hold-down strap member can also be included and be can pivotally interconnected with the saw's base for movement between a storage position and a hold-down position in releasable engagement with the saw's drive assembly in order to releasably secure the drive assembly in a lowered storage position relative to the base.
Also, the operator handle of the saw preferably includes a horizontally extending gripping portion that is generally centered laterally with respect to the plane of the blade or cutter. This contributes advantageously to workpiece visibility, ease of use, and operator control of the saw or other cutting device so equipped.
Other advantages, objects and features of the present invention will become apparent to those skilled in the art from the subsequent detailed description, appended claims and accompanying drawings.